Model making



R. S. MEGATHLIN.

MODEL MAKING.

APPLICATION FILED AUG-1.1921.

Patented May 23, 1922.

2 SH ETS-SHEET 1..

R S. MEGATHLIN.

MODEL MAKING.

APPLICATION FILED AUG. 1, 1921.

Patented May 23, 1922.

2 SHEETSSHEET 2.

MAM/Hm- 3.2

,1 TED RALPH s. MEGATHLIN, or SOMERVILLE,

MASSACHUSETTS. ASSIGNOR TO UNITED TION OF NEW JERSEY.

Specification of Application filed August 1 To-aZZ whom it may concern: v

Be it known that I, RALPH S. MEGATHLIN, a citizen of the United States, and residin at Somerville, in the county of Middlesex an State of Massachusetts, have invented certain Improvements in Model Making, of which the following description, inconnection with the accompanyingdrawings, is a specification, like reference characters on the drawings indicating like parts in the.

. several figures.

This invention relates to last making and is illustrated in connection with the production of a set of lasts or, more exactly, models. It is the present custom to turn lasts in a last lathe, which is one form of the copying lathe, using a model which is reproduced in the work. The machine is provided with two substantially pantagraphic mechanisms called graders to modify the longitudinal and lateral dimensions of the model as desired, independently. It being required to turn a set of, for example, womens lasts comprising a regular run of sizes and widths from a single-model, the fundamentals of the grading are substantially as follows:

The lasts having the same nominal width, that is, the 4-13 (model), I-B, 5-B, 6-B, etc.', are substantially geometricall similar solids, increasing inch'in lengt and 1: inch in perimeter at the waist for each length size unit. These increments will be found to result in a substantially uniform rate of increase in all directions, though theremay be actually a small'discrepancy between the length and width magnification factors, and the discrepancy varies somewhat, owing to the custom of making lasts of the same marked size of various actual lengths to secure differences in style of toe tip.

- the plane. In other words, their toe springs and heel springs have been altered by the magnification from the original model. This condition of things is undesirable for several reasons, among which are;

(1) Human feet do not vary in size and MODEL MAKING.

Letters Patent. Patented May 23, 1922.

, 1921. Serial N0. 488,860.

form in this manner, and the lasts fail to fit'equally well throughout the series.

\ (2) The appearance of different shoes of -the set varies so much as to affect disadvantageously the retailing problem.

(3) The differences in height and wedge of-heel required throughout the set constitute a serious shoe manufacturing difilculty.

Thisgeneral problem is dealt with in various ways, according to the expense to which the shoe manufacturer is willing to go. The best solution of it in general use, prior to the present invention, involves making one or more (generally three) models in each width, for example, a 1, 4 and 7 in each width. These models are corrected, after being produced by grading in the last lathe in the ordinary way, by bending them at the waist or the ball, to change the relation between the toe tip, heel corner and ball point, in order to correct the springs and make the whole series more uniform. This is done by splitting the last from the top and bottom so deep that the slits nearly meet, and wedging one slit until the other closes. This whole operation has to be performed by.a skilled model maker, and is entirely empirical. It is very expensive, cannot be done certainly twice alike, and at itsbest, only a small fraction of the lasts in, the set are right, since all the lasts graded from these corrected models, that is, those which are not duplicates of them, will be affected with the original difiiculty, only to a smaller extent.

It is an important object of the present invention to provide a solution for this problem which will be more economical than the present practice. practically satisfactory, and which will avoid the objections mentioned, among others. I contemplate turning the entire-set of lasts from a set-of modified models, all of the same foot room, but having their toes attached to the main body at varying angles, these angles being accurately chosen so that the standard model thus modified will, in each case, grade exactly into the last which it is desired to produce with it. models thus characterized form important features of the invention; The members of the set will all measure the same size and width but the line joining the toe tip and ball tread point will make varying angles with the line from the ball tread point to the heel corner. throughout the set. In the illustrated embodiment of the invention a set of preferably interchangeable toe pieces is used. attached to the main body at varying angles. and such a set of apparatus forms an important feature of the invention. The invention also provides a definite systematic way of ascertaining predeterminedly the required angles of bend in the standard t-B for womens) model in order to produce the desired results, and accordingly the improvement in methods of last production which consists in ascertaining the required model distortion, distorting the model correspondingly and then grading directly from the distorted model to produce the result desired, constitutes an important aspect of the invention.

These and other aspects of the invention will be better understood from the following description of a preferred embodiment thereof taken in connection with the accompanying drawings, in which,

Fig. 1 illustrates diagrammatically the model and its set of toe pieces.

Fig. 2 is a diagram showing generally how to determine the bending angles of the models.

Fig. 3 is a diagram showing how to determine the bending angles for the special case of lasts of the same width.

Fig. 1 shows diagrammatically a model 10 have a secant face 13, preferably at or about the waist, to which various toe pieces 11, 12 shown in dotted lines may be firmly attached in any desired or convenient man-- ner. These toe pieces are equal in number to the models which are to be used to develop the whole system of lasts, and are built on to the original model waist at varying angles such that when graded they will yield the result desired.

The single waist and back part and the set of toe pieces are thus the equivalent of a like number of models with corrected spring. I shall show herein how these toe pieces may be developed accurately and systematically without the expense of the skilled model makers judgment, the proper angles of cut for the toes being determined by analytic rather than empirical methods. This set of model apparatus I regard as an important feature of the invention.

Fig. 2 is a diagram developing the general solution of the bending problem.

PSKIHCBQ is the central "ertical longitudinal section of the original model. and B is the bending point, taken arbitrarily. TQD is the floor line. BT is (here) drawn from B through the toe tip P to meet the floor line in some point T. In some instances it may be well to draw BT so as to pass a little above or below I as a certain amount of toe spring variation can be effected in this way as will be seen. In Fig. 2 the model is bent by swinging the toe tip down about the oint B, through an angle 3 The fi ure T SQR then takes the position T,P R, and the angle of bend, y, is TBT,. The line T,H, is taken as the axis of rotation in the lathe. This line does not pass through the toe tip P, in the drawing, owing to the fact that the last shown as an actual toe spring, and the analysis is much simplified by working from the point T,, ever, slight variations in positions of models on their mechanical axes of rotation frequently occur in practice, as it is difficult to pick out any definite location for the heel dog. If the length and width grading factors are equal, it makes no difference at all. If they are not, in theory a slight distortion results from such a tipping, but is never noticed in practice.

The bent model P,H will now be graded, using, however. T, as a fixed origin. The length grading factor will be called L, and the width grading factor W. The graded position C of any point C is found by finding its projection E on the axis T,H,, taking T,E:La2(T,E), and erecting the perpendicular E'C':VV00(EC). The floor line may be located by the points G, and G in the same way, and all desired points of the last similarly plotted.

From the above it is obvious that W tan s= tan r (1) The heel spring of the graded last is CD length as T,H, in order to bring out the length grade, and is easily seen to be near enough. Since the heel of the last is on a curve, EH and EH, will be sensibly equal, and as already stated, a small variation in position of the axis in a model is of small moment. In the drawing the angle TBT, is exaggerated, and the distance HH, is really very small. The difference between TE, T,E, is also negligible. This artifice simplifies the analysis, and involves no error of importance in wood work.

In effecting a direct solution of the problem, the known elements are L, \V, the distances TE:T,E, EC, all data relating to the point B, such as the distances TB, BE. and angle TBE, the angles tzBTQ IBTJQ, and the original model heel spring instead of the toe tip. How- (It should be noticed that we do not know TE and EC and the angle TBE exnear ehough), or can be corrected in advance in the light of experience. EC can be accepted as measured on the original model. It may be remarked at the same time that we have described T as swung from T around B, and also called TE;- T,E. Practically the error involved in this is not discernible in woodwork. Any necessary allowance could be made in the sawing for the separable toe-piece, in order to bring out the overall lengths the same).

By means of equation (2) in which everything on the right is known except 8, we can determine the angle 8 so as to make the graded heel spring CD anythin we like, for example equal to the original D. This equation can be solved by trial and error with a table of natural or logarithmic sines and cosines, or reduced to algebraic form by the substitution sin 1 cos Having determined 8 .we can determine the angle 1' by the equation The angle 2 is then given by In the triangle T BE we now know T E, BE, and z; and

' sin 2 which is the result sought.

The toe spring of the original model PH has been altered slightly by the grading, due to the facts that the point P, is not on the grading axis T H and that the angle of the floor line with this axis is changed by the grade. A proper arrangement of the line ET in regard to the point P, in the light of experience, will effect a certain amount of control of this feature. In the example of Fig. 2, both of the enumerated causes increase the toe spring of the graded last. If theline BT had been drawn above the point P to such an amount that the point I, would have fallen below T H,, the toe spring could have been kept unchanged.

The simpler special problem of the set of lasts having the same width will now be developed. As already stated, these lasts are substantially geometrically similar sol ids. Any one can therefore be developed from the model by selecting a point as :a pole, and magnifying all radii vectors drawn from the point to the model surface, in the same proportion. In the actual cutting of such a last in the lathe, the longitudinal and lateral magnifications are entirely independent and at right angles to each other, but under our fundamental (and somewhat inaccurate) hypothesis, the result is substantially as stated.

Fig. 3 shows at abcdefg the central longitudinal profile of the 4-B model. We are to determinehow to bend it in order that the bent 4-13 model will grade into another required B last. We first select the axis of the bend. (This point B, here, as well as the general problem, is preferably always taken in the waist at a place wherethe upper and lower contours are about arallel, as bending the model about this point will not tend to cause troublesome steps at b and f on the upper and lower surfaces.) In Fig. 3 the point B selected is on the line oae, joining the toe tip a and lower heel corner 0. The floor line is shown at oh, the toe spring at at, and the heel spring at eh. 66 is drawn parallel to the floor line. The graded last should have its lower heel corner on this line in order to preserve the overall heel height unchanged.

Let G be the magnification factor. Locate e on ee so that 0e:Grm(0e). Locate 6 on 0e 50 that 06 206. In the drawing G has been grossly exaggerated in order to make the drawing clear. Its value is approximately 1.35, which would grade a 4-13 up to about a l l-B. Even with this exaggeration Be and Be, would differ only by about .02 inch on a full size scale, so that we can assume that Be Be,.

If, then, we bend down the body of the last about the point B, leaving the toe in position, the distorted last takes the position abc,d,e,fg. Magnify the distorted last by the factor G, which can be done b multiplying all radii vectors through by G, and the magnified last will take the position a'b'c'def'g and will obviously have the same overall heel height as the original model abcdefg. The toe spring, at, has been changed to aft. This discrepancy is small; is exaggerated in the drawing like everything else, and on the shoe-itself will be hardly noticeable.

The angle of bend is 6136 and has thus been found graphically. If e" is the point where eh cuts 06', this angle will obviously differ from eBe by an amount too small to be measurable on wood and e"h:e h, within a like degree of accuracy. The value of 136" is easily found. Let X'zeh, the desired overall heel height, and let Xzeh, the model overall' heel height. Then 6 h and may be called F, and the angle Bee,

Be is known which may be called 5, is known from the original data of the last. Applying the trigonometric formula 1 1) (Ali 4k a" (080] we have II F 00t- B6 Txy- 008d) .4. G:

It will be noticed that nothing in the above analysis depends upon the point 6 being the lower heel corner, so that it has really been shown how to bend the model so as to maintain the height of any point of the tread surface unchanged when grading a last from another of the same marked width. The formula (6) is also true generally for cases where X and X are not equal. Similarly the results developed in regard to Fig. 2 are equally general, except that the initial approximations relative to the position of the point E are weakened by moving C toward the toe. The process, in brief. is to plot the desired result. which is simple when the magnifying factor is the same in all directions, grade it inverselyin order to obtain the model which must be directly graded from in order to produce it, and compare this model with the originally given model.

The formulae developed above determine the angles through which the original -B model must be bent in order to grade into a last having the desired sole profile. The proper number of 4-13 models may be prepared by duplication of the first one in the. last lathe, their toes cut off in accordance with these angles and joined to back parts 10 (Fig. 1) corresponding to the zero angle of cut. If the joining means is separable one back part will serve for the whole series, but the speed ordinarily necessary in getting out a last order will require the use of several machines at once.

These models are produced without the expensive skilled-labor-cut-and-try method, the work is predeterminedly exact, and can be duplicated exactly at any future time.

Models can be made corresponding to every size and width, so that a perfectly accurate set of lasts can be produced.

Having described my invention, what I claim as new and desire to secure by Letters Patent of the United States is 1. That improvement in methods of manufacturing lasts which consists in providing a set of models all of the same style, size and width, but having their forward and rearward portions joined at varying angles, and cutting lasts from these models in the last lathe, by means of the length and width graders.

' '12. That improvement in methods of manufacturing lasts which consists in turning in the last lathe, by ordinary length and Width grading, a last of desired size and Width from a model distorted by the introduction of a bend calculated to modify the effect of the grading upon the sole profile of the normal model.

That improvement in methods of manufacturing lasts which consists in turning in the last lathe by ordinary length and Width grading, a last of the desired size and width from a model having an abnormal relation between the toe tip, heel corner and-ball point, to modify the effect of the grading upon the sole profile of the normal model.

1. A set of model apparatus comprising a standard rear part and a set of toe parts identical except for a varying wedge at their rear ends, and all constructed and arranged to fit the rear part.

A set of model apparatus comprising a standard rear part, a standard toe part, and a set of other parts identical with one of said parts except for the addition or subtraction of Wedges of varying angularity at the joints, all the members of the set being constructed and arranged to fit the said standard part of differing species to form a bent model.

6. A last part constructed and arranged to fit interchangeably a set of last parts .of complementary species to form a set of variably bent models of the same size and width.

7. A' set of last models of the same size and width differing among themselves by a systematic series of bends. whereby any one of the set can be directly length-and-widthgraded in the last lathe to produce a last of a predetermined profile characteristic.

8. A last model of standard size and width differing from the standard model of that style by a bend between its forward part and its rear part, the bend being determined in connection with an assumed grade to produce a graded last having a predetermined profile characteristic.

9. A last model of standard size and width differing from a standard model of that style by a bend determined substantially in accordance with formula (5) of the annexed specification.

10. That improvement in the art of producing from a model a graded object having anomalous variation from an object regularly graded from the model, which consists in plotting an anomalous graded result desired, grading it inversely, distorting the model to correspond with the inversely graded object, and then grading from the distorted model directly to the o'b'ect desired.

11 testimony whereof I have signed my name to this specification.

RALPH S. MEGATHLIN.

Certificate of (Correction,

It is hereby certified thet in Letters Patent No. 1,417 2 74, granted May 23, 1922, upon the application of Ralph S. Megathlin, of Someri ille, Massachusetts, for an improvement in Model Making, errors appear in the printed specification requiring correction as follows: Page 1, line 77, for theword splitting read slitting; page 2, lines 93, 94, 105, and page 3, line 95, strike out the letter x and insert the multiplication sign X; and that the said Letters Patent should be read with these corrections therein that the same may conform to the recordv of the case in the Patent Oflice.

Signed and sealed this 7th day of November, A. 1)., 1922.

[5mm] KARL FENNING,

Q Acting} Commissioner of Patents. 

